In recent years, illegal use, as represented by so-called spoofing, has been increasing rapidly in the World Wide Web (WWW)-mediated services, such as Internet banking services, on-line stores, or the like.
For example, in the case of Internet banking, in addition to the systems in which user authentication is performed by making use of a banking organization-issued random number table that is unique to each user, systems in which user authentication is performed by making use of, for example, a one-time password generated by a cryptographic token issued by the banking organization (for example, Patent Document 1), have been put to practical use.